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API MPMS 11.1.7 1980 (R1987) – Temperature Correction for API Gravity of Generalized Petroleum Products
Essential Principles and Compliance Considerations for Accurate Density Measurement in Hydrocarbon Custody Transfer
Scope and Application
API Manual of Petroleum Measurement Standards (MPMS) Chapter 11.1.7, originally published in 1980 and reaffirmed in 1987, provides standardized tables for correcting observed API gravity of generalized petroleum products to 60°F (15.56°C). This standard is part of the comprehensive API MPMS Chapter 11.1 series dedicated to temperature and pressure volume correction factors. It specifically addresses the thermal expansion behavior of hydrocarbon liquids classified as “generalized products,” which include gasoline, kerosene, diesel fuels, fuel oils, and similar refined middle distillates.
The scope of API MPMS 11.1.7 covers observed API gravity corrections within a temperature range from 0°F to 150°F (–18°C to 66°C) and for products having API gravity at 60°F between 0° and 100° API. The correction tables are based on experimentally determined thermal expansion coefficients of typical petroleum fractions and were originally derived from the International Critical Tables and supplementary research conducted by the API and ASTM. The standard is widely used in custody transfer metering, inventory control, pipeline operations, and regulatory reporting to ensure that API gravity (and consequently density) is reported at the standard reference temperature of 60°F.
Note: As of 2026, the 1980 edition remains a reference for legacy systems and regulatory frameworks in many jurisdictions. However, for new applications, users should refer to the current (2001 and later) editions of API MPMS 11.1, which provide updated correlation equations (including Generalized, Crude, Lubricating Oil tables) based on the GPA/API/ASTM joint research.
Technical Requirements: Correction Tables and Calculation Methodology
API MPMS 11.1.7 provides a set of correction tables labeled Table 7A and Table 7B (commonly referred to as the “Generalized Products – API Gravity Correction Tables”). The correction factor, denoted as fg, is applied to the observed API gravity to obtain the corrected API gravity at 60°F:
API@60°F = APIobs + Correctionf
Table 7A provides additive corrections for observed API gravity, while Table 7B provides corrections in units of degrees API per degree Fahrenheit of temperature difference. The standard instructs the user to locate a base correction factor corresponding to the temperature and observed API gravity, and then apply any necessary interpolations.
| Observed Temp. (°F) | API Gravity at 60°F | Correction Factor (°API) | Thermal Expansion Coefficient β (per °F) |
|---|---|---|---|
| 30 | 40.0 | +1.27 | 0.000565 |
| 50 | 40.0 | +0.42 | 0.000565 |
| 70 | 40.0 | –0.42 | 0.000565 |
| 90 | 40.0 | –1.27 | 0.000565 |
Tip: When observed API gravity is not listed exactly in the tables, users should perform linear interpolation between the two nearest entries. The 1987 reaffirmation confirmed that this interpolation method remains acceptable for the accuracy required in commercial transactions.
Key Parameters
- Reference Temperature: 60°F (15.56°C).
- Applicable Product Classes: Generalized products (gasoline, naphtha, kerosene, diesel, fuel oils). Not for crude oils (use API MPMS 11.1.3) or lubricating oils (use API MPMS 11.1.5).
- Temperature Range: 0°F to 150°F (with limited extrapolation allowed but not recommended).
- API Gravity Range: 0° to 100° API at 60°F.
Implementation: Using the Correction Tables
To apply the standard correctly, the operator must first obtain a representative sample of the product and measure its API gravity at the observed temperature using a hydrometer or digital density meter in accordance with ASTM D1298 or D4052, respectively. The observed temperature is noted simultaneously. Using the temperature and the observed API gravity, the operator enters the appropriate correction table.
The correction factor from the table is added algebraically to the observed API gravity. For example, if the observed API gravity is 45.5° at 80°F, the table correction might be –0.85° API, yielding an API gravity of 44.65° at 60°F. After correction, the API gravity can be used to calculate density or specific gravity using the standard API/ASTM relation or the ASTM D1250 tables.
Caution: The correction factors provided in API MPMS 11.1.7 are derived for “generalized products” assuming a fixed thermal expansion coefficient curve. Using these tables for crude oils or lubricating oils will introduce errors because those products have different volumetric behavior with temperature. Always verify the product classification before applying the tables.
Interpolation Guidelines
When the exact observed API gravity does not appear in the table, linear interpolation is performed across the API gravity range for the given temperature. Similarly, if the observed temperature falls between temperature increments, interpolation is applied between the correction factors at the two bounding temperatures. The standard explicitly recommends rounding the final corrected API gravity to 0.1° API for custody transfer.
Compliance and Regulatory Notes
API MPMS 11.1.7 is referenced in various national and international regulations, including the U.S. Customs and Border Protection guidelines for petroleum imports, the IRS regulations for alcohol fuel mixtures, and many state-level weights and measures laws. It is also harmonized with the international standards ASTM D1250/IP 200, which provide equivalent temperature correction tables. In 1987, the API reaffirmed this standard without technical changes, indicating its continued acceptance in the industry.
For new measurement installations, the latest editions of API MPMS Chapter 11.1 (e.g., 11.1-2001, 11.1 Addendum 2009) have superseded the 1980/1987 edition. However, legacy systems and long-term supply contracts often still reference the 1980 edition, and it is essential for compliance officers and metering specialists to be familiar with both versions to resolve measurement discrepancies.
Important: Failing to apply the correct temperature correction can lead to systematic errors in volume and mass determination. For example, a 1° API error at 60°F can translate to a 0.5% error in mass calculation for a typical crude oil cargo. Custody transfer applications require strict adherence to the specified correction method.
Comparison with Later Editions
The 1980 edition uses discrete lookup tables with integer API gravity and temperature increments. The 2001 edition introduces algorithmic equations (fits) that can be used in electronic flow computers, reducing interpolation errors. Nevertheless, the 1980 edition is still acceptable for manual calculations and verification of electronic computations.
Frequently Asked Questions
Q: Can API MPMS 11.1.7 1980 (1987) be used for crude oil correction?
A: No. Crude oils require the use of API MPMS 11.1.3 (Crude Oils – Correction to 60°F) which uses different thermal expansion coefficients derived specifically for crude oil. Using the generalized product tables for crude oil will result in significant errors.
A: No. Crude oils require the use of API MPMS 11.1.3 (Crude Oils – Correction to 60°F) which uses different thermal expansion coefficients derived specifically for crude oil. Using the generalized product tables for crude oil will result in significant errors.
Q: What is the difference between API MPMS 11.1.7 and ASTM D1250?
A: Both standards provide equivalent temperature correction tables for generalized products. API MPMS 11.1.7 is the API version, while ASTM D1250/IP 200 is the joint ASTM/IP version. The correction factors are identical; the choice typically depends on contractual and regional preferences.
A: Both standards provide equivalent temperature correction tables for generalized products. API MPMS 11.1.7 is the API version, while ASTM D1250/IP 200 is the joint ASTM/IP version. The correction factors are identical; the choice typically depends on contractual and regional preferences.
Q: Is the 1987 reaffirmation change the content of the 1980 edition?
A: No. The reaffirmation indicates that the standard was reviewed and retained without substantive technical changes. Therefore, the 1980 and 1987 editions are identical in content.
A: No. The reaffirmation indicates that the standard was reviewed and retained without substantive technical changes. Therefore, the 1980 and 1987 editions are identical in content.
Q: How do I convert the corrected API gravity to density at 60°F?
A: Use the standard formula: Density (lb/gal) = 141.5 × (0.999012 + 0.00000656 × API) / (131.5 + API) at 60°F. Alternatively, use API MPMS 11.1.5 for density conversion tables.
A: Use the standard formula: Density (lb/gal) = 141.5 × (0.999012 + 0.00000656 × API) / (131.5 + API) at 60°F. Alternatively, use API MPMS 11.1.5 for density conversion tables.